Electrochemical cell electrode

ABSTRACT

A supported catalyst useful in the preparation of an electrode for an electrochemical cell which comprises the residue remaining after heating at about 500 DEG  to about 700 DEG  C. a transition metal and a polymer such as polyvinylpyridine all adsorbed on a support material. Useful electrodes are prepared by combining the supported catalyst with a current collector.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to catalytic electrodes for electrochemicalcells.

2. Description of the Prior Art

The term "fuel cell" is used herein and in the art to denote a device,system, or apparatus in which the chemical energy of a fluid combustiblefuel such as hydrogen, carbon monoxide, or an organic compoundcontaining hydrogen in its molecular structure is electrochemicallyconverted to electrical energy at a nonsacrificial or inert electrode. Acomplete fuel cell is adapted for continuous operation and is suppliedwith both fuel and oxygen from sources outside the cell proper. Suchcells include at least two nonsacrificial or inert electrodes,functioning as an anode and a cathode, respectively, which are separatedby an electrolyte which also provides ionic conductance therebetween.There is also provided conduction means for electrical connectionbetween anode and cathode external to the electrolyte, means foradmitting a liquid or gaseous fuel into dual contact with the anode andelectrolyte, and means for admitting oxygen in dual contact with thecathode and electrolyte. The electrolyte compartments in conventionalfuel cells are divided into an anolyte and a catholyte compartment by anion permeable partition or ion exchange membrane, such as in the solidpolymer electrolyte, also known as a proton exchange membrane (PEM) typefuel cell. In this PEM type cell, the membrane, which is a solidpolyelectrolyte, acts both as the electrolyte and the cell separator,thus requiring no additional electrolyte. This cell is also termed anion exchange membrane type fuel cell. In each such cell, a fuel isoxidized at the anode and an oxidant is reduced at the cathode uponreceiving electrons from the anode.

Electrodes of the type hereinbefore and hereinafter described are alsoemployed in electrolytic cells which unlike the aforementioned fuelcells do not provide a net production of electrical energy, but in whichan organic fuel is oxidized electrochemically at the anode thereof. Insuch cells, a direct current of electrical energy from an externalsource, namely a fuel cell, a storage battery or an alternating currentrectifier, is admitted to the electrical circuit of the cell to providethe necessary electrical current to operate the cell. Such cells can beused for the electrochemical production of various organic chemicals,such as the conversion of alcohols or hydrocarbons to ketones.

Electrodes for use in these cells vary considerably in both design andcomposition. Although a single metal structure, such as a platinum sheetor screen, or a structure of porous carbon, such as a flat sheet or aporous carbon cylinder, can be used alone, electrodes commonly comprisea conductive base or current collector with a metal catalyst chemicallyand/or physically bound to the surface of the base. Such electrodes alsoinclude those upon which the catalyst is laid down byelectro-deposition, and those which are impregnated with catalyst bysoaking the base in a solution comprising a suitable catalyst yieldingmaterial, decomposing the adsorbed material and/or reducing theresulting metal-containing material to elemental metal or metal oxide.The latter technique is conventional in the preparation of porous carbonelectrodes bearing a metal catalyst. Noble metals, particularlyplatinum, are effective catalysts in both oxidation-reduction reactionswherein either a basic or acid electrolyte is employed in the cell.

The use of monomeric, as well as, polymeric metal phthalocyaninecompounds as oxidation catalysts for chemical reactions are known. Forexample, nickel phthalocyanine has been employed in the oxidation oflong-chain fatty acids, esters, saturated ketones, benzene hydrocarbons,etc. Such catalysts, particularly cobalt phthalocyanine, when used as anactive component in the cathode of a fuel cell are advantageous overknown electrode catalysts comprised of noble metals, primarily in thatthe cobalt phthalocyanine catalyst is relatively inexpensive and can beproduced in any desired amount. One disadvantage of electrodescomprising cobalt phthalocyanine is that this compound has an extremelylow conductivity in comparison with noble metal catalyst compositionsand, therefore, such metal phthalocyanine catalyst must be applied invery thin layers upon the surfaces of conducting carrier material in thepreparation of electrodes. Electrochemical cells having electrodescomprising cobalt phthalocyanine, are disclosed in U.S. Pat. No.3,585,079 and U.S. Pat. No. 4,255,498. Heat treated, carbon supportedmetalloporphyrins and metallophthalocyanines as oxygen reductioncatalysts are disclosed in J. Chem. Society; Faraday trans. 1, 77,2827-2843 (1981).

It is conventional to prepare electrodes for electrolytic cells bymixing powdered or granular active carbon particles which act as acarrier or support material for the adsorbed catalyst layer. Suchelectrodes are prepared by mixing the catalyzed carbon particles with awater-repellent binder such as polytetrafluoroethylene and compressingthe mixture into a thin sheet.

SUMMARY OF THE INVENTION

There are disclosed novel metal catalysts for use in the preparation ofelectrodes for electrochemical cells, preferably, fuel cells forconverting hydrogen and oxygen to energy. The novel catalyst can beadsorbed on an electrically conductive support or contact material, suchas metal, graphite, or carbon powders heated at about 500° C. -800° C.,and mixed with a water-repellent binder, such as a fluorinatedhydrocarbon polymer, for instance, polytetrafluoroethylene, and,thereafter, coated directly or indirectly onto a current collector suchas a carbon fiber paper as steps in the process of making an assemblysuitable for use as an electrode. The novel catalyst, support or contactmaterial, and binder can also be coated onto a non-porous substrate andthe coating transferred to an electrically conductive material servingas a current collector, such as, carbon fiber paper or a nickel screenor transferred to a solid polymer electrolyte membrane.

When the metal or carbon support material and catalyst are mixed with awater-repellent binder, such as polytetrafluorethylene, and the mixturecoated onto a current collector, such as carbon fiber paper, theassembly can be bonded on the catalyst coated side of the carbon fiberpaper to an ion exchange membrane using heat and pressure so as to formone embodiment of an electrode of the invention useful in a solidpolymer electrolyte electrolytic cell.

The supported catalysts of the invention provide results comparable tothat of the cobalt phthalocyanine catalyst of the prior art and are, inaddition, significantly less expensive than this catalyst andsubstantially less expensive than the known supported catalystscomprised of noble metals, such as, platinum black. Instead of cobalt,iron, platinum, and ruthenium can be used in other embodiments of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

One embodiment of the catalyst of the invention is prepared by adsorbingonto a finely divided metal, carbon, or graphite, preferably, powderedor granulated active carbon, a solution containing a metal salt, suchas, at least one or a mixture of metal salts, or metal alloys thereof,selected from the salts of transition metals in admixture withpoly(4-vinylpyridine). Other useful polymers includepoly(2-vinylpyridine), poly(ethyleneimine), and poly(4-aminostyrene).Useful transition metal salts include metals such as iron, cobalt,nickel, molybdenum, chromium, manganese, tungsten, titanium, zinc,copper, cadmium, and vanadium. Other useful metals include the noblemetals platinum, palladium, and ruthenium.

The concentration of the metal salt and polymer, for instance,poly(4-vinylpyridine) in solution is controlled so that the coating ofthe support material takes place from (1) an all organic solvent or (2)a mixed organic solvent and an aqueous solvent solution of the metalsalt and poly(4-vinylpyridine), which is not precipitated. Generally,organic solvents such as methanol, ethanol, 1-propanol, and 2-propanolare utilized to dissolve the polyvinylpyridine. Water is used todissolve the metal salt. The atomic ratio of metal salt to one of thepyridine repeating units of the polyvinylpyridine is, generally, about0.001 to 1.0, preferably, about 0.01 to 0.5, and, most preferably, about0.05 to 0.25. The ratio of metal salt to the support material is,generally, about 0.01 to 50 grams, preferably, about 0.1 to 5 grams,and, most preferably, about 0.5 to 2.5 grams per gram of supportmaterial.

In the preparation of one embodiment of the supported catalyst of theinvention on a carbon support, subsequent to soaking the carbon powderin a solution of metal salt and, for instance, poly(4-vinylpyridine),the coated carbon support material is filtered and the solvent isevaporated. The coated carbon support assembly is then heated todecompose the poly(4-vinylpyridine). Generally, heating is conducted atabout 500-800 degrees centigrade, preferably, about 600° to 700° C., andmost preferably, at about 650° to 690° C., under a nitrogen atmospherefor about 3-5 hours. Subsequently, the catalyst adsorbed on the carbonsupport can be applied from a mixture of catalyst and a water-repellentbinder, such as, polytetrafluoroethylene to coat a current collectorsubstrate such as a carbon fiber paper on one side. Coating can beaccomplished using a metering bar, metering rod, or a coating knife.

As an alternative to direct coating of the catalyst on a currentcollector substrate, the aqueous dispersion of binder and the supportedmetal poly(4-vinylpyridine) catalyst complex can be coated onto asmooth, non-porous surface such as niobium foil and, subsequently,transferred to a current collector such as a metal screen or carbonfiber paper, by the use of heat and pressure. Coating can beaccomplished using a coagulated or non-coagulated aqueous dispersioncomprising a polytetrafluoroethylene binder. The dispersion can becoagulated utilizing at least one of the following methods, i.e., theaddition of a water miscible organic solvent or the raising of thetemperature of the dispersion slightly above ambient temperature. Thecoating of the smooth non-porous surface is accomplished utilizing acoating rod, or bar or knife, as is conventional in this art. Successiveapplications may be required to obtain the desired coating thickness.For use in cells characterized as solid polymer electrolyte electrolyticcells, the coated side of individual catalyst coated carbon fiber papersheets can be bonded to both sides of an ion exchange membrane.

As a substitute for the preferred poly(4-vinylpyridine), additionalmonomeric compounds or alternative polymers, which can function suitablyto take the place of the preferred poly(4-vinylpyridine), can be used.These can be defined as monomeric or polymeric compounds containing anitrogen-containing functional group in which the nitrogen has a lonepair of electrons which can form a coordination complex with a metalion.

When an electrode is prepared utilizing an ion exchange membrane, themembrane can be, preferably, selected from the two broad classes ofcation exchange resins; the so-called sulfonic acid cation exchangeresins and the carboxylic acid cation exchange resins. In the sulfonicacid membranes, the cation ion exchange groups are hydrated sulfonicacid groups which are attached to the polymer backbone by sulfonation.In the carboxylic acid resins, the ion exchanging group is COO⁻.

The preferred ion exchange membranes are disclosed in U.S. Pat. No.4,478,695 and U.S. Pat. No. 4,470,889, incorporated herein by reference.These materials, on an equivalent weight basis, generally hydrate lesswhen immersed in water at the boil, in accordance with prior arthydration procedures, than the sulfonated perfluorocarbon membranes soldunder the trade designation NAFION. At equivalent weights which arebetter for ion transport, i.e., lower equivalent weights provide lowerelectrical resistance in the cell, the membranes described in the '695and '889 patents can be hydrated to absorb about 40-50% by weight basedupon the dry weight of the membrane. These more suitable membranes wouldhave equivalent weights of about 750-1000.

A typical proton exchange membrane (PEM) assembly can be made by firsthydrating the ion exchange membrane and subsequently bonding a catalystlayer thereto utilizing heat and pressure. Generally, the hydration ofthe membrane is accomplished by first converting the membrane from thesalt form to the proton form. The salt form (usually the sodium orpotassium salt) is thus converted by placing it in a strong acidsolution, such as sulfuric acid. Subsequently, the membrane is washedand boiled. Water of hydration is incorporated into the membrane byheating it at a temperature of about 160-210 degrees centigrade,preferably by pressing the membrane. Subsequently, the membrane isexposed to water at room temperature up to the boiling point. Themembrane/electrode assemblies are subsequently prepared by combining thehydrated proton form of the membrane with an electrode layer. Theelectrode layer is prepared in accordance with one embodiment of thisinvention by bonding to carbon fiber paper a previously heat treatedmetal polyvinylpyridine catalyst on a supporting carbon particle using awater-repellent fluorinated hydrocarbon binder, such as,polytetrafluoroethylene. As the last step in the preparation of themembrane/electrode assembly, a hydrated ion exchange membrane is bondedby pressing at elevated temperature to a catalyst-coated currentcollector. Bonding is generally accomplished at a temperature of about160-210 degrees centigrade. Alternatively, the previously heat treatedmetal polyvinylpyridine catalyst materials of one embodiment of theinvention can be deposited directly upon the surface of an ion exchangemembrane in the form of finely-divided particles or powders, such assupport material metal powders or finely-divided granular or powderedcarbon. Although the particle size of the supported catalytic materialis not critical, a preferred range of particle size is from about25-1000 angstrom units.

Since the catalytic particles upon the surface of the solid polymerelectrolyte membrane must be energized for the passage of current forthe electro oxidation or electro reduction of chemicals and elements,for the passage of current through the solid polymer electrolytemembrane, and the like, the catalyst particles or powder must be of thetype generally classified as conductive, that is, such catalystparticles or powder must be electrically conductive.

As used herein, finely-divided means any powder form, particulate form,granular form, bead form, or any other form of catalyst or supportmaterial which may be deposited upon a carbon fiber paper, a non-poroussupport, or a solid polymer electrolyte membrane. The amount of catalystmaterial which is deposited directly or indirectly upon the surface ofthe carbon fiber paper or on the solid polymer electrolyte membranes inaccordance with the process of the present invention, is not critical.The catalytic particles must be fixed upon the surface of the carbonfiber paper or alternative current collector or solid polymerelectrolyte membrane. Any well known fixing technique of adhering,bonding or otherwise uniting a particulate or powdered material to asurface may be used. In the prior art, bonding of electrode layers isdisclosed at temperatures up to 177 degrees centigrade. Catalyticparticles or powder may be fixed upon the surfaces of the carbon fiberpaper or solid polymer electrolyte membrane by any one or a combinationof pressure, heat, adhesive, binder, solvent, electrostatic means, andthe like. The preferred embodiment for fixing the particles of catalystupon said surfaces is by a combination of pressure and heat.

The following examples illustrate the various aspects of the inventionbut are not intended to limit its scope. Where not otherwise specifiedthroughout this specification and claims, temperatures are given indegrees centigrade and parts, percentages, and proportions are byweight.

EXAMPLE 1

The catalyst of the invention was deposited on a carbon powder inaccordance with the following procedure. To a rapidly stirred 25milliliter methanol solution of 0.8 gram poly(4-vinylpyridine) per 100milliliters of methanol, said poly (4-vinylpyridine) having a molecularweight of 4.9×10⁵, there are added 25 milliliters of a 10 millimolar,aqueous solution of cobalt chloride containing 0.1 molar sodium acetateas a buffer to maintain the pH at about 5.5. To this solution, there areadded 2 grams of carbon powder sold under the trade designation XC-72 bythe Cabot Corporation. Stirring of the solution is continued untiluniform and then the solution is filtered and the solvent evaporated.Thereafter, the carbon powder having the cobalt chloride andpoly(4-vinylpyridine) deposited thereon is heated to 650-690 degreescentigrade under a nitrogen atmosphere. The carbon is, thereafter,slowly cooled under a nitrogen atmosphere.

EXAMPLE 2

Using the carbon supported catalyst of Example 1, an aqueous coatingdispersion containing polytetrafluoroethylene as a binder was preparedand, thereafter, a coating was applied to a carbon fiber paper toproduce an electrode in accordance with the following procedure.

The electrode fabrication consists of two steps, first, the carbon fiberpaper is wet proofed by coating with an aqueous dispersion ofpolytetrafluoroethylene and, thereafter, a coating of the carbon powderand cobalt polyvinylpyridine is formed on the surface of a niobium foilby the application of a mixture of 70 percent by weight of the carbonsupported catalyst prepared in Example 1 with 30 percent by weight ofpolytetrafluoroethylene latex sold under the trade name Teflon T-30 byDuPont. After drying, the coating was transferred to the wet proofedcarbon fiber paper by pressing the wet proofed carbon fiber paperagainst the coated surface of the niobium plate at a pressure of about1000 psi and a temperature of about 40° C. for 2-7 minutes. Thereafter,the assembly was heated in an oven at 350° C. for 5 minutes. Aftercooling at ambient temperature, the assembly was placed in water and theniobium foil was slowly peeled away to leave a catalyst coating on thewet proofed carbon fiber paper. The final electrode assembly wasprepared by bonding a perfluorosulfonic acid membrane of 837 equivalentweight to the coated side of the wet proofed carbon fiber paper bypressing at 500 psi and 177° C. for 5 minutes.

In wet proofing the carbon fiber paper, a polytetrafluoroethyleneloading of approximately 10-15 mg per square centimeter was used. As isapparent, the polytetrafluoroethylene in the electrode catalyst layerserves the purpose of preventing the catalyst particles from being wetby the electrolyte when the electrode is used in an electrochemicalcell. Such wetting would degrade the performance of the electrode bypreventing the oxygen gas from reacting readily with the catalyst. Ifthe catalyst particles are wet by the electrolyte, the oxygen gas wouldbe required to diffuse through a layer of electrolyte, thus, slowing thereaction considerably.

The carbon fiber paper used in the preparation of the electrode is soldunder the trade name PC-206 by The Stackpole Fibers Company. This is ahigh porosity carbon fiber paper having a porosity rating ofapproximately 80%. The paper used is typically 14 mils in thickness.

EXAMPLE 3

The solid polymer electrolyte electrode of Example 2 was placed in atest fuel cell as described in the Experimental section of an articleentitled "Oxygen Reduction in a Proton Exchange Membrane Test Cell", Theauthors of which include two of the joint inventors of this application,said article appearing in the J. Electrochemical Soc. Vol. 135, No 7,Jul. 1989, incorporated herein by reference. Determinations of voltagefor various current densities were obtained utilizing the electrode asthe cathode in said test fuel cell. The initial operating conditions forthe cell were as follows: 10 pounds per square inch oxygen pressure, 85°relative humidity, oxygen flow rate of 27 cubic centimeters per minute.The test results are shown in Table I and in FIG. 1, curve A incomparison with an electrode similarly prepared (as indicated inExamples 4-6) and utilized in a fuel cell in which cobalt phthalocyaninewas used as a catalyst on a carbon support.

Generally, the electrochemical test cell apparatus consists of apotentiostat/galvanostat which is used to supply current between thecatalytic electrode of a membrane/electrode assembly and a platinum wirewhich is used as the counter-electrode. The potential between thecatalytic electrode and the calomel reference electrode at the appliedcurrent was determined using the potentiostat/galvanostat. Themembrane/electrode assembly was placed between two portions of the testcell which were then clamped together. The top portion of the test cellis used as a sulfuric acid reservoir to provide a source of protons tobe transported through the membrane and consumed in the porouselectrode. The bottom portion of the test cell is used to supply oxygento the porous electrode. Oxygen gas is flowed into the bottom portion ofthe test cell. The membrane/electrode assembly consists of a membrane, aporous backing layer made of teflon-impregnated carbon fiber paper and acatalytic layer made of a mixture of carbon-supported catalyst and apolytetrafluoroethylene binder. Platinum gauze was placed beneath thecarbon fiber paper of the electrode-membrane assembly to serve as thecurrent collector. Purified oxygen is fed to the test cell by way of ahumidifier in which the oxygen gas is bubbled through a containerpartially filled with water. The gas pressure in the test cell isregulated and monitored utilizing a pressure gauge. A rotameter is usedto measure the gas flow rate.

EXAMPLE 4-6 (Controls, Forming No Part of This Invention.)

Utilizing cobalt phthalocyanine as a catalyst, the procedure of Examples1-3 was followed in order to prepare and test an electrode in order todetermine performance characteristics in a fuel cell of a prior artcatalytic electrode in comparison with the inventive electrode ofExample 2. Results of Example 6 are shown in the Figure.

EXAMPLE 7

Example 2 is repeated using the supported catalyst of Example 1 exceptthat the supported catalyst mixture of Example 1 andpolytetrafluoroethylene latex is coagulated prior to coating the mixtureonto niobium foil. The coagulated mixture was prepared by diluting theTeflon T-30 latex with 50 milliliters of water and subsequently addingthe cobalt polyvinylpyridine/carbon supported catalyst with continuousstirring. The coagulum was formed by adding 2 to 3 drops of 2-propanolwhile stirring until a coagulum was formed. The coagulum can also beinduced more quickly by warming the solution to about 60° C. Subsequentto decanting the solvent, the coagulum obtained is rinsed with waterseveral times and, thereafter, the coagulum is coated onto a niobiumfoil and allowed to dry. The electrode is then prepared in accordancewith the remaining procedure of Example 2. Test results are shown in theTable.

EXAMPLE 8

This example describes the preparation of an iron poly(4-vinylpyridine)catalyst supported on carbon powder.

An aqueous solution of 20 millimolar iron (III) chloride containing 0.4molar sodium acetate as a buffer (pH 5.5) in the amount of 12.5milliliters was combined with 12.5 milliliters of an aqueous solution of100 millimolar NH₂ OH HCl (hydroxyammonium chloride) to reduce iron(III) to iron (II). After the solution becomes clear, stirring wascontinued for 20 minutes and then the mixture was filtered. The clearfiltrate was mixed with an equal volume of 0.8 grams per 100 millilitersof poly(4-vinylpyridine) dissolved in methanol while stirring rapidly toeffect the solution of the iron polyvinylpyridine complex.

A supported catalyst utilizing carbon as a support was prepared inaccordance with the procedure of Example 7 except that the ironpolyvinylpyridine/polytetrafluoroethylene binder weight ratio was 50/50on a percent by weight basis. The performance of this catalyst, whenutilized in the test cell described in Example 3, is detailed in theTable below.

EXAMPLE 9

This example describes the preparation of a platinumpoly(4-vinylpyridine) catalyst supported on carbon powder.

A platinum salt, (NH₄)₂ PtCl₄ in the amount of 24 milligrams was addedto 12.5 milliliters of a solution of poly(4-vinylpyridine) in methanolcontaining 0.8 grams of polymer per 100 milliliters of methanol. Themixture was filtered and methanol was added to bring the total volume to25 milliliters. Carbon powder sold under the trade name XC-72 by CabotCorporation was added to this mixture and the mixture stirred for 4hours. Thereafter, the solution was filtered and theplatinum/polyvinylpyridine supported on the carbon powder was heattreated at a temperature of 650°-690° C. under an inert atmosphere. Anelectrode assembly was prepared in accordance with the procedure ofExample 2 utilizing 70% by weight of the supported catalyst with 30% byweight of the polytetrafluoroethylene dispersion. Test results are shownin the Table.

EXAMPLE 10

This example describes the preparation of a ruthenium (bipyridine)₂chloride-poly(4-vinylpyridine) catalyst supported on a carbon powder.

Ruthenium (bipyridine)₂ Cl₂ in the amount of 33 milligrams, containing 2molecules of water of hydration, was slowly dissolved in hot methanolunder a nitrogen atmosphere. After degassing the mixture, 12.5milliliters of a solution of poly(4-vinylpyridine) in methanolcontaining 0.8 grams of polymer per 100 milliliters of methanol wasadded to the solution of the ruthenium salt with stirring. The solutionwas heated at reflux for 1/2 an hour and then 1 gram of a carbon powdersold under the trade name XC-72 was added with stirring. Aftercontinuing stirring for 30 minutes, the methanol was slowly evaporatedto deposit the ruthenium polyvinylpyridine complex on the carbon powder.

An electrode assembly was prepared in accordance with the procedure ofExample 2 except that the solvent utilized to prepare the catalystcoating mixture was NaBr:H₂ O:acetone 30:55:15 on a volume basis. Thecatalyst coating mixture contained 70% by weight of the supportedcatalyst and 30% by weight of polytetrafluoroethylene dispersion.

The test results of this electrode in the test cell described in Example3 are reported in the Table.

                  TABLE                                                           ______________________________________                                        Performance of Electrodes of the Invention in a Test Cell                                            Volts                                                                Current  (vs. standard                                          Example (Metal)                                                                             (mA/cm.sup.2                                                                           Hydrogen Electrode)                                    ______________________________________                                         2 (Cobalt)    10      0.441                                                                100      0.242                                                                500      0.085                                                                1000     0.056                                                   7 (Cobalt)    10      0.498                                                                100      0.300                                                                500      0.088                                                                1000     0.032                                                   8 (Iron)      10      0.474                                                                100      0.272                                                                500      0.203                                                                1000     0.170                                                   9 (Platinum)  10      0.747                                                                100      0.612                                                                500      0.422                                                                1000     0.317                                                  10 (Ruthenium)                                                                               10      0.326                                                                100      0.175                                                                500      0.073                                                                1000     0.038                                                  C-36,619                                                                      ______________________________________                                    

The procedure of Examples 1, 2, and 7 is repeated utilizingpoly(2-vinylpyridine) substituted for the poly(4-vinylpyridine) utilizedin Examples 1, 2, and 7. Upon evaluation of the electrodes prepared inthis manner, these electrodes show substantialelectroactivity for oxygenreduction.

EXAMPLES 14-16

Examples 1, 2, and 7 are repeated utilizing poly(ethyleneimine)substituted for the poly(4-vinylpyridine) utilized in Examples 1, 2, and7. Upon evaluation of the electrodes prepared in these examples, theseelectrodes show substantial electroactivity for oxygen reduction.

EXAMPLES 17-19

Examples 1, 2, and 7 are repeated utilizing poly(4-aminostyrene)substituted for the poly(4-vinylpyridine) utilized in Examples 1, 2, and7. Upon evaluation of the electrodes prepared in these examples, theseelectrodes show substantial electroactivity for oxygen reduction.

EXAMPLES 20-22

Examples 8 through 10 are repeated substituting poly(2-vinylpyridine)for the poly(4-vinylpyridine) of Examples 8 through 10. Upon evaluationof the electrodes prepared in these examples, these electrodes showsubstantial electroactivity for oxygen reduction.

EXAMPLES 23-25

Examples 8 through 10 are repeated substituting poly(ethyleneimine) forthe poly(4-vinylpyridine) utilized in Examples 8 through 10. Uponevaluation of the electrodes prepared in these examples, theseelectrodes show substantial electroactivity for oxygen reduction.

EXAMPLES 26-28

Examples 8 through 10 are repeated substituting poly(4-aminostyrene) forthe poly(4-vinylpyridine) utilized in Examples 8 through 10. Uponevaluation of the electrodes prepared in these examples, theseelectrodes show substantial electroactivity for oxygen reduction.

While this invention has been described with reference to certainspecific embodiments, it will be recognized by those skilled in the artthat many variations are possible without departing from the scope andspirit of the invention. It will be understood that it is intended tocover all changes and modifications of the invention disclosed hereinfor the purposes of illustration, which do not constitute departuresfrom the spirit and scope of the invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A supported transitionmetal or noble metal catalyst useful in the preparation of an electrodefor an electrochemical cell comprising a support material and a residueremaining after heating under an inert atmosphere at a temperature ofabout 500 to about 700 degrees centigrade of a mixture of a transitionor noble metal salt and a polymer selected from the group consisting ofpoly (4-vinylpyridine), poly(2-vinylpyridine), poly (ethyleneimine), andpoly (4-aminostyrene).
 2. The supported catalyst of claim 1, whereinsaid transition metal is selected from iron, cobalt, nickel, molybdenum,chromium, manganese, tungsten, titanium, zinc, copper, cadmium, andvanadium, said noble metal is selected from the group consisting ofplatinum, palladium, osmium, ruthenium, and iridium.
 3. The supportedcatalyst of claim 2, wherein said transition metal is selected from thegroup consisting of cobalt and iron and said support material is ametal, carbon, or graphite.
 4. An electrode for an electrochemical cellcomprising a current collector, a mixture of a water-repellent binderand a support material having adsorbed thereon a transition metal ornoble metal catalyst comprising a transition or noble metal salt and apolymer selected from the group consisting of poly (4-vinylpyridine),poly (2-vinylpyridine), poly (ethyleneimine), and poly (4-aminostyrene)wherein said electrode is prepared by the process comprising treatingsaid support material with a solvent solution of a mixture of atransition metal or noble metal salt and said polymer, removing saidsolvent, and heating said mixture under an inert atmosphere at atemperature of about 500 to about 700 degrees centrigrade.
 5. Theelectrode of claim 4, wherein said transition metal is selected from thegroup consisting of iron, cobalt, nickel, molybdenum, chromium,manganese, tungsten, titanium, zinc, copper, cadmium, and vanadium, saidnoble metal is selected from the group consisting of platinum,palladium, ruthenium, osmium, and iridium, said support material is ametal, carbon, or graphite, said current collector is carbon fiberpaper, and said binder is a fluorinated hydrocarbon.
 6. The electrode ofclaim 5, wherein said transition metal is cobalt or iron said noblemetal is platinum or ruthenium, and said binder ispolytetrafluoroethylene.
 7. An electrochemical cell comprisingelectrodes consisting of an anodic electrode, a cathodic electrode, andan electrolyte and at least one of said electrodes comprising a currentcollector combined with a layer of a mixture of a binder and atransition metal or noble metal catalyst on a support material, saidcatalyst comprising a residue remaining after heating at about 500 toabout 700 degrees centigrade of a mixture of a transition or noble metalsalt, a polymer selected from the group consisting of poly(4-vinylpyridine), poly (2-vinylpyridine), poly (ethyleneimine), andpoly (4-aminostyrene).
 8. The electrochemical cell of claim 7, whereinsaid support material is a metal, carbon, or graphite and said binder isa fluorinated hydrocarbon polymer.
 9. The electrochemical cell of claim8, wherein said binder is polytetrafluoroethylene and said cell is afuel cell for the conversion of hydrogen and oxygen.
 10. The fuel cellof claim 9, wherein said transition metal is selected from the groupconsisting of iron, cobalt, nickel, molybdenum, chromium, manganese,tungsten, titanium, zinc, copper, cadmium, and vanadium, and said noblemetal is selected from the group consisting of platinum, palladium,ruthenium, osmium, and iridium.
 11. The fuel cell of claim 10, whereinsaid transition metal is cobalt or iron, said noble metal is platinum orruthenium and said support material is powdered or granular activecarbon.